1. Field of the Invention
The present invention relates to silver-containing films which develop upon being heated. In particular, the present invention relates to the use of a silver sulfonate as a physical developer in heat-developable films.
2. Discussion of the Prior Art
Heat-developable or photothermographic films ordinarily contain a silver salt, a photocatalyst, a reducing agent, and binder as the major components. The photocatalyst is usually a silver halide. The silver salt serves as a physical developer by supplying the silver which forms the visible image; the prior art has placed particular emphasis on the use of silver behenate and silver benzotriazole.
Silver alkanesulfonic acid salts are described in photopolymerizable and heat developable, compositions in U.S. Pat. Nos. 3,347,676 and 3,529,963. These patents do not suggest that such combinations would be applicable in silver halide speed thermographic films. U.S. Pat. No. 4,069,759 discloses silver 2-aminoethane sulfonate in a polyvinyl butyral dry process and silver system used for an electrostatic printing plate master. Japanese Patent Publication JA 52/018308 describes the use of silver fluoroalkane sulfonate in a dry silver system activated by infrared radiation.
In spite of the numerous publications in the field of heat-developable silver films, an enabling disclosure is lacking on how to employ novel physical developers such as silver sulfonates in such a system.